Check for two_phase change at end of process_syncing_tables_for_apply.

Previously this function checked to see if we were ready to switch
to two_phase mode at its start, but that's silly: we should check
at the end, after we've done the work that might make us ready.
This simple change removes one sleep cycle from the time needed to
switch to two_phase mode.  In the real world that might not be
worth much, but it shaves a few seconds off the runtime for the
subscription test suite.

Nathan Bossart

Discussion: https://postgr.es/m/20221122004119.GA132961@nathanxps13

diff --git a/src/backend/replication/logical/tablesync.c b/src/backend/replication/logical/tablesync.c
index 2fdfeb5b4c9d08f59c9151342a0677f48206f105..09b3e8b32ac59f4846fc68ed7797b10b183e4706 100644 (file)
--- a/src/backend/replication/logical/tablesync.c
+++ b/src/backend/replication/logical/tablesync.c
@@ -415,6 +415,7 @@ process_syncing_tables_for_apply(XLogRecPtr current_lsn)
    static HTAB *last_start_times = NULL;
    ListCell   *lc;
    bool        started_tx = false;
+   bool        should_exit = false;
 
    Assert(!IsTransactionState());
 
@@ -446,28 +447,6 @@ process_syncing_tables_for_apply(XLogRecPtr current_lsn)
        last_start_times = NULL;
    }
 
-   /*
-    * Even when the two_phase mode is requested by the user, it remains as
-    * 'pending' until all tablesyncs have reached READY state.
-    *
-    * When this happens, we restart the apply worker and (if the conditions
-    * are still ok) then the two_phase tri-state will become 'enabled' at
-    * that time.
-    *
-    * Note: If the subscription has no tables then leave the state as
-    * PENDING, which allows ALTER SUBSCRIPTION ... REFRESH PUBLICATION to
-    * work.
-    */
-   if (MySubscription->twophasestate == LOGICALREP_TWOPHASE_STATE_PENDING &&
-       AllTablesyncsReady())
-   {
-       ereport(LOG,
-               (errmsg("logical replication apply worker for subscription \"%s\" will restart so that two_phase can be enabled",
-                       MySubscription->name)));
-
-       proc_exit(0);
-   }
-
    /*
     * Process all tables that are being synchronized.
     */
@@ -619,9 +598,36 @@ process_syncing_tables_for_apply(XLogRecPtr current_lsn)
 
    if (started_tx)
    {
+       /*
+        * Even when the two_phase mode is requested by the user, it remains
+        * as 'pending' until all tablesyncs have reached READY state.
+        *
+        * When this happens, we restart the apply worker and (if the
+        * conditions are still ok) then the two_phase tri-state will become
+        * 'enabled' at that time.
+        *
+        * Note: If the subscription has no tables then leave the state as
+        * PENDING, which allows ALTER SUBSCRIPTION ... REFRESH PUBLICATION to
+        * work.
+        */
+       if (MySubscription->twophasestate == LOGICALREP_TWOPHASE_STATE_PENDING)
+       {
+           CommandCounterIncrement();  /* make updates visible */
+           if (AllTablesyncsReady())
+           {
+               ereport(LOG,
+                       (errmsg("logical replication apply worker for subscription \"%s\" will restart so that two_phase can be enabled",
+                               MySubscription->name)));
+               should_exit = true;
+           }
+       }
+
        CommitTransactionCommand();
        pgstat_report_stat(true);
    }
+
+   if (should_exit)
+       proc_exit(0);
 }
 
 /*
@@ -802,6 +808,7 @@ fetch_remote_table_info(char *nspname, char *relname,
        TupleTableSlot *tslot;
        Oid         attrsRow[] = {INT2VECTOROID};
        StringInfoData pub_names;
+
        initStringInfo(&pub_names);
        foreach(lc, MySubscription->publications)
        {